Diodes & transistors worksheet with answers

Free printable Diodes & transistors worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
+−20 V150 Ω6.2 VIR​ = ?

A 6.2 V Zener diode is fed from 20 V through a 150 Ω resistor, with no load connected. Find the current IR in the resistor.

Vin = 20 VVZ = 6.2 VR = 150 Ω
IR = mA
2.Easy
+−Vs​10 VR = 4.7 kΩD1​D2​I = ?

A 10 V DC source drives current through a 4.7 kΩ resistor in series with two forward-biased silicon diodes. Use the constant-drop model with 0.7 V per conducting diode. Find the current I in mA.

Vs = 10 VR = 4.7 kΩVD = 0.7 V
I = mA
3.Medium
+−9 V100 Ω3.3 V1500 ΩIZ​ = ?

A 3.3 V Zener regulator is fed from 9 V through 100 Ω and supplies a 1500 Ω load. Find the Zener current IZ.

Vin = 9 VVZ = 3.3 VR = 100 ΩRL = 1500 Ω
IZ = mA
4.Medium
+−24 VR = ?5 × 2.2 V20 mA

5 green LEDs (forward voltage 2.2 V each) are connected in series with a resistor to a 24 V supply. Find the resistance R that sets the current to 20 mA.

Vs = 24 VVF = 2.2 Vn = 5I = 20 mA
R = Ω
5.Hard
+−≥ 20 VR = ?5.6 V≤ 30 mA

A 5.6 V Zener regulator must supply up to 30 mA to a load. The input can drop to 20 V, and the Zener needs at least 2 mA to regulate. Find the largest series resistance Rmax that keeps it regulating.

Vin,min = 20 VVZ = 5.6 VIL,max = 30 mAIZ,min = 2 mA
Rmax = Ω
6.Hard
V (V)I (mA)0.65627.27Q = ?

A diode is modelled as 0.65 V in series with 10 Ω (it conducts above 0.65 V). It is in series with a 220 Ω resistor across a 6 V supply. Find the operating current ID where the diode line meets the load line.

Vs = 6 VR = 220 ΩV0 = 0.65 Vrd = 10 Ω
ID = mA

Answer key

  1. 1. IR = 92 mA
  2. 2. I = 1.83 mA
  3. 3. IZ = 54.8 mA
  4. 4. R = 650 Ω
  5. 5. Rmax = 450 Ω
  6. 6. ID = 23.26 mA

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